The present invention relates to new intermediates for preparing corticoidal compounds, and a process for their preparation.
It is known to prepare .DELTA..sup.16 -20-keto steroids by heating the corresponding 17.alpha.-acyloxy steroids in dimethylformamide in the presence of potassium acetate [Salce et al., J. Org. Chem. 35: 1681 (1970)]. However, a prerequisite for effecting this reaction is that acyloxy residues be present in the 21-position as well as in the 17.alpha.-position. That is, for example, under the same conditions, if 17.alpha.-acetoxy-4-pregnene-6.alpha.-methyl-3,20-dione is heated, the acyloxy group in the 17.alpha.-position is not split off, whereas 17.alpha.-acetoxy-21-hydroxy-4-pregnene-3,20-dione yields, under transacylation, the 21-acetate, without, however, acquiring a .DELTA..sup.16 -double bond [Solo et al., J. Org. Chem. 45: 2012 (1980)].
If the substituent in the 21-position is a chlorine atom rather than the hydroxy group, the result likewise is no .DELTA..sup.16 -elimination product under these reaction conditions (Solo, loc. cit.).
It is furthermore known that, by applying the aforementioned reaction conditions to 11.beta.,17.alpha.-dinitrooxy-21-acetoxy-20-keto steroids, the corresponding unsaturated .DELTA..sup.9(11),16 -21-acetoxy-20-keto steroids are obtained (DOS [German Unexamined Laid-Open Application] 2,236,115, whose disclosures are incorporated by reference herein).
A direct procedure for the production of .DELTA..sup.9(11) - and .DELTA..sup.16 -unsaturated 21-chloro steroids, however, is not known.